freopen用法
#include <bits/stdc++.h>
using namespace std;
int main()
{
freopen("1.in","r",stdin);
freopen("1.out","w",stdout);
int n;
scanf("%d",&n);
printf("%d\n",n);
fclose(stdin);//关闭重定向输入
fclose(stdout);//关闭重定向输出
return 0;
}

